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. 2020 Jun 27;119(3):690–704. doi: 10.1016/j.bpj.2020.06.022

Figure 2.

Figure 2

Fit of ISK I/V plots from rSK2 overexpressed in rat VCMs with I/V plots predicted from the model. (A) Normalized ISK/voltage and bulk [Ca2+]int./voltage (right) for VCMs expressing wild-type rSK2 under control conditions (left) or treated with isoproterenol (ISO; 100 nM, middle). ISK was normalized to the maximal current amplitude for the same cell under ISO conditions. The solid line indicates the I/V plot predicted by the model for the baseline (black) and ISO (red) conditions. ISK recordings from wild-type rSK2 control show a biphasic relation dependent on Vm reaching a peak at 25–30 mV because of the SK channel’s rectification characteristics. ISO stimulation alleviated the inhibition of ISK at higher voltages, showing a continuous increase of ISK with Vm. Note different levels of IntR for the wild-type ISO plot. n = 4–7; N = 4–5; mean ± SE. rSK2 wild-type plots were replotted from raw data published in Hamilton et al. (38). (B) Normalized ISK/voltage and bulk [Ca2+]int/voltage (right) for VCMs expressing mutant rSK2 (R396E-K397E), which has no IntR (Li and Aldrich (30)). The solid lines indicate predicted the I/V plot for the baseline and ISO conditions as in (A). n = 11; N = 5; mean ± SE.